Spatial and Temporal Control of Molecular Interactions in Surfactant Systems

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ABSTRACTIntellectual Merit: This project is an investigation that aims to useredox-active surfactants and electrochemical methods to achieve spatial and temporalcontrol over the interactions of surfactants with DNA. The study is motivated by theinvestigators recently published observation that manipulation of the oxidation state offerrocenyl surfactants can be used to control transfection of cells.The first goal of the research is to use light scattering and neutron scattering measurements to determine how the interactions of DNA with surfactants containing the redox-active group ferrocene depend on the oxidation state of the ferrocene: ferrocene undergoes a reversible one electron oxidation from an electrically neutral state to a charged (+1) state. The surfactants to be studied incorporate two ferrocene groups and undergo a change in charge from (+1) to (+3) upon oxidation of the ferrocene. We hypothesize that changes in the oxidation state of the ferrocene will lead to substantial changes in electrostatic interactions between the surfactants and DNA and thus changes in the sizes and microstructures of complexes formed by these species.The second goal of the research described in this proposal is to understand thetransport and self-assembly processes that occur near electrodes immersed into aqueoussolutions of ferrocene-containing surfactants. By using a thin film electrochemical cell,the investigator will investigate the influence of the dynamics of surfactant self-assembly processes as well as the influence of interactions between the surfactants with added DNA on the properties of solutions within 100 of an electrode.The results of the above two studies, when combined, would provide principles for achieving spatial and temporal control over the formation of complexes between DNAand ferrocene-containing surfactants.Broader Impacts: The studies described in this proposal will provide understanding in how spatially localized changes in the oxidation states of redox-active surfactants at electrodes impact their association with biological molecules such as DNA. These topics are intellectually rich ones that will broadly advance our understanding of molecular interactions in surfactants and biomolecular systems. In addition, it addresses the relatively poorly understood topic of dynamics in surfactant systems. As describedabove, the investigators have already shown that the oxidation state of ferrocenylsurfactants can have a dramatic effect on the transfection of cells, i.e., the delivery of DNA to cells. Knowledge of the interactions of these surfactants with DNA, as well as knowledge of the fundamental factors that govern the generation of localized changes in the properties of these solutions near electrodes, will enable further development of these novel principles for control of transfection as well as a number of other potential applications (protein crystallization, microscale separations, meso-scale materials synthesis). The research provides exciting opportunities for ongoing the education of two female graduate students through projects that combine colloid chemistry, interface engineering (Abbott), biomolecular and materials engineering (Lynn) and fluid mechanics/mass transport phenomena (Graham). The students will be presented with the unusual opportunity of being able to experience both discovery oriented experimental research as well as complementary numerical modeling and analysis. Because of the reduction of the original budget, the expected results and scope have been reduced to the first stages of the overall project.